Issue |
EPL
Volume 98, Number 1, April 2012
|
|
---|---|---|
Article Number | 10012 | |
Number of page(s) | 6 | |
Section | General | |
DOI | https://doi.org/10.1209/0295-5075/98/10012 | |
Published online | 12 April 2012 |
Polarons and dressed molecules near narrow Feshbach resonances
ICFO - The Institute of Photonic Sciences - 08860 Castelldefels (Barcelona), Spain, EU
Received:
7
December
2011
Accepted:
9
March
2012
The properties of impurities immersed in a large Fermi sea are naturally described in terms of dressed quasiparticles: attractive and repulsive polarons, and dressed molecules. Motivated by recent experiments on narrow Feshbach resonances, we analyze here how the quasiparticle properties are affected by a non-zero resonance range. We find two interesting analytic results. For large range, the ground-state energy close to resonance is shown to become perturbative in the inverse range. In the limit of broad resonance instead, we provide a new Tan's relation linking the impurity ground-state energy E↓ to the number of atoms in its dressing cloud ΔN. As a corollary, at unitarity one finds ΔN=−E↓/ϵF, with ϵF the Fermi energy of the bath.
PACS: 03.75.Ss – Degenerate Fermi gases / 05.30.Fk – Fermion systems and electron gas / 71.10.Ca – Electron gas, Fermi gas
© EPLA, 2012
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